Resilient centering device for concentric cylindrical members



Dec. 1, 1959 w. HORSTING, sR' 2,915,089-

RESILIENT CENTERING DEVICE FOR CONCENTRIC CYLINDRICAL MEMBERS Filed March 24, 1958 J. is

United States Patent 1 .1. .0 RESILIENT CENTERING DEVICEFOR; CONCEN- TRIC CYLINDRICAL ME BERS.

William F. HorstingQ Sn, Wilmette, Ill., assignor of twenty-five percent to Ira Milton Jones, Milwaukee, Wis. I v

Application March 24,1958, Serial No. 723,583 2 Claims. (Cl. 13887) This invention has as its general objective the provision of means for yieldingly opposing relative shifting in any radial direction between a pair of spaced concentric inner and outer cylindrical members. In a more specific sense this invention relates to the provision of improved resilient centering means for use in oil well installations to minimize radial shifting of the well tubing out of concentricity with'respect to the casing surrounding it. g

7 In an oil well installation the pump rod operates within tubing which in turn is housed within acasing, in radially spaced relation to the casing. The tubing is comprised of pipes, usually thirty feet long, connected in end to end relation by couplings or collars, and in deep wells the tubing may be as much as several thousand feet long.

' As is well known, theweight of thecolumn ofoil in the tubing of an operating oil well causes the tubing to be severely stressed on each lift stroke of the pump rod. These intermittent stresses tend to cause the tubing to be sinuously whipped laterally back and forthin its casing, and thusresult in distortion of the tubing out of a desired state of concentricity with respect to its casing and the pump rod. Moreover, such gyration of the tubing increases in magnitude and violence in proportion to the length of the tubing. 7

In the absence of means for counteracting this tendency for the tubing to whip about laterally in its casing, there is apt to be serious binding of the pump rod in the tubing and rapid wearing of the rod and of thetubing itself due to the elongation of the tubing that takes place simultaneously with lateral gyratory motion of the tubing againstthewalls of its casing.

Various centering devices have-been proposed in the past to minimize or even prevent such gyration of the tubing of an oil well in its casing, but those which are capable of functioning in a satisfactory manner are nevertheless objectionable for several reasons. Some interfere with removal of'the'tubing from its casing, as must be done fromtime to time; others are large and heavy, and"thus"difliculttohandle; and most of them involve the use of special means to secure them to the tubing or in the casing therefor. The greatest deterrent to widespread use of conventional'centering devices, however, is one of cost. When it is appreciated that the more successful conventional centering devices are priced at from $28.00 to $42.00 per unit, and that as many as 100 or more of such units spaced along the length of the tubing would be required to adequately hold the tubing centered in a deep Well, the cost of equipping wells with such centering devices becomes nearly prohibitive.

In contrast, it is one of the purposes of this invention to provide a centering device which is especially well suited to maintain the tubing employed in an oil well properly centered within its casing and which, moreover, can be manufactured and sold for but a small fraction of the cost of conventional centering devices.

In this connection it is a more specific purpose of this invention to provide a centering device of the character 2,915,089 Patented Dec. 1, 1959 2 described which is made from a single length ofcspring wire wound to provide coaxial endwise adjacent large and small diameter groups of coils respectively of a size to engage within the casing of an oil well and around the tubing in the casing to normally hold the tubing concentric with the casing and to strongly'resist shifting of the tubing in any radial direction within the casing.

It is a furtherpurpose of this invention to provide a resilient centering device which, though primarily intended for use in oil wells to hold the tubing coaxially within its casing and minimize radial shifting of the tubing in the casing, is applicable to any pair of spaced concentric inner and outer cylindrcal members to yieldingly hold the same in'conce'ntric relation.

With the above and other objects in view which will appear as the description proceeds, this invention resides in the novel' construction, combination and arrangement ofparts substantially asihereinafter described and 'more particularly defined by the appended claims, it being understood that such changes. in the precise embodiment of the hereindisblosed invention may be made as come within the scope'of the claims. t

The accompanying drawing illustrates one complete ex ample of the physical embodiment of the inventionlconstructed according to the best mode so far devised for the practical application of the principles thereof, and in which:

Figure 1 is a view partly in side elevation and partly in section and showing the application of a centering device of this invention to the tubing of mod well; and Figure 2 is a perspective view of the resilient centering device per se. Y i I Referring now tothe accompanying drawing, the numeral 5 designates the casing of an oil well, andjthe numeral 6 the tubing which extends down through the casing in radially spaced relation thereto. The tubing, as iscustomary, is comprised of endwise connected lengths ofpipe 7 joined at their adjacent ends by a coupling .or collar 8 into which the pipes thread. -Also asis customary, the pump rod 9 of the well extends downwardly through the tubing 7 and in theoperation ofthe well it is vertically reciprocated in order to pump oil up' through the interior of the tubing 6. r

The centering device 10 of this invention is comprised of a length of spring wire wound toprovide groups of coaxial, closely. endwise adjacent large and small diameter coils. In the form of the invention chosen for illustration, the centering device has been wound to provide, a pair of coaxial endwise spaced groups of coils 11 of large diameter to fit theinterior of the casing, and 'a smaller diameter intermediate group of coils 12 coaxial with the end groups 11 andof a size to fit the exterior of the tubing 6. The end convolutions 13 of the smaller diameter group of coils 12 are integrally connected with the adjacent end convolutions 14 of the large diameter groups of coils 11 by substantially spiral shaped lengths of wire 15.

The intermediate group of coils 12 is comprised of a number of convolutions of uniform diameter, which may be directly axially contiguous to one another or spaced apart slightly if desired, and they collectively embrace a substantial expanse of the exterior of the tubing 7 in substantially snug relationship. Each of the end groups of coils 11 is adapted to have engagement with a considerable axial expanse of the wall of the casing 5, and comprises a number of convolutions of a uniform large diameter which may be either directly axially contiguous or spaced slightly apart if desired. With this arrangement the groups of helical convolutions in effect provide collars which have sufficient axial length as to render the groups of coils substantially stable against twisting or tilting of the groups of convolutions out of..eoaxial relation with one another and withrespect to the axis of the tubing and its casing.

While in the present case, the small diameter group :of vcoils 12 'is.-;shown comprised of seven Lconvolutions -and-.=each.of the'larger diameter-end groups ,ofcoils '11 is shown comprised of'three convolutions, the number of convolutions which comprise the different groups 'of coils .may be varied as desired. In fact, the' number :and arrangement of groups of coils may also be increased andualtered in any desired fashion, for example, to provide two ormore groups of axially spaced small diameter convolutions to engage around the tubing. 6 at locations spaced sufliciently'far apart as to provide for the reception of integrally connected larger diameter groups of -coils between; such smaller diameter groups.

'Preferably'one resilient annular centering device-such as shown in the drawings is mountedon each thirty-foot length'of pipe'7 of which the tubing'6 is comprised. The small diameter groups of coils 12 may be slipped on over the lower end of a length of pipe 7 prior to threading-it into the collar orcoupling 8 by which two adjacent'lengths of pipe are joined together. The collar or coupling 8 thus provides an abutment at its upper end upon which the lowermost of the smaller diameter groups of coils 12 may seat to hold the centering device against downward-displacement on the tubing.

Thus, with one centering device such as illustrated encircling the lower end of each thirty-foot length of pipe and seatedsagainst the adjacent end of the collar connecting adjacent lengths of pipe. it will be ap reciated that the centering devices of this invention will beaccurately spaced apart at thirty-foot intervals upon the tubing 6, without the need for special means to secure the devices to the tubing.

It will also be appreciated that thespring wire from which the-centering device is wound shouldhave a suf- "ficiently large cross section as to provide groups of coils -11 and 12 of substantial rigidity to at all times tend to hold the tubing 6 coaxially within its casing and to strongly but yieldingly oppose the tendency of the tubing to shift laterally in its casing due to the stresses imposed on the tubing during the lift strokes of the'pump rod.

"In other wordsywhile the centering devices of this invention are intended to minimize lateral deflection of the tubing '6, they are preferably resilient and yielding to the extent of providing-for slight lateral shifting of the tubing under the influence of severe stresses. Thus,

the-centering devices act'to absorb shocks which might are wound close together as shown.

groups of connected coils cooperate with one another and with the tubing and casing between which they are confined, in such a way that deflection of the tubing 6 in any radial direction is strongly opposed and minimized.

As stated previously the convolutions which comprise the diflerent groups of coils 11 and 12 may be spaced apart any desired small but uniform distance, but maxim..m resistance to-relative radial shifting of the groups of coils during use of the device, is achieved when the coils Also, manufacture of the device at low cost is facilitated when the coils are clo ely wound.

From the foregoing description taken together with the accompanying drawing it will be readily apparent to those skilled in the art that this invention provides a resilient annular centering device which is not only capable of functioning to minimize lateral deflection of the tubing of an oil well out of concentricity with respect to the well casing, but that it is also capable of manufacture and sale at low cost.

What is claimed as my invention is:

1. In a well installation, the combination of: a tube of indeterminate length, through which fluid may be pumped; a cylindrical casing of indeterminate length surrounding thetube in spaced relation thereto; and a series of resilient annular members coaxial with the casing and interposed between it and the tube at spacedintervals, and through all of which members the tube extends, formaintaining the tube substantially, concentric with the casing and for cushioning lateral whipping of the tube in consequence of stresses attending the pumping of fluid therethrough, each of said resilient members comprising a single length of spring wire wound to provide three integrally connected coaxial coils which are unconfined in their axial dimension and closely axially adjacent, two of said coils being substantially identical and axially spaced apart, and each of said two coils being comprised of a plurality of adjacent convolutions of the same diameter, the third coil being intermediate said two coils and being comprised of a plurality of adjacent convolutions of a second diameter; the smaller of said convolutions substantially closely encircling the tube and the larger convolutions having their .peripheriescontiguous to the casing so as. to yieldingly resist-lateral shifting of the smaller convolutions and the tube' encircled thereby out of coaxial relation with the casing.

-2. In:a well :installation, the combination set forth in claim 1 furthercharacterized by the fact that the intermediate coil of each annular member has the convolutions of smaller diameter.

References Cited in the file of this patent UNITED STATES PATENTS 2,498,042 Kolber Feb. 21, 1950 2,512,116 Siebels June 20, 1950 2,851,157 Christman Sept. 9, 1958 FOREIGN PATENTS 103,337 .Switzerland Feb. 16, 1924 

